Storing Biomass for Renewable Energy Production

As the use of agricultural land to grow biomass for renewable energy production increases in conjunction with increasing global demand for food, it is becoming more and more important to produce high-yield bioenergy crops with a good energy-balance.

Sugar beet is a high-yielding crop, has a good energy-balance, and is well suited as a feedstock for biogas production through anaerobic digestion. For sugar beets to be used as a feedstock for biomass renewable energy, suitable storage methods are required so that sugar beets harvested in the fall can be used as a feedstock for biogas production year-round.

Researchers at the Swedish Institute of Agricultural and Environmental Engineering (JTI) have recently completed a study to assess the potential to silo sugar beets for use year-round. For this research, 4,000 tonnes of whole sugar beets were ensiled, while another 200 tonnes of chopped sugar beets were co-ensiled with chopped straw.

Year-Round Availability

The research found that during the ensiling process, the volume of whole sugar beets decreased by almost 40%, and seepage from the silo was noted after only one week; seepage was greatest during the following three weeks. Furthermore, while a moderate temperature rise is normal during silage, a sharp increase in temperature was measured from the ensiled sugar beets, and this temperature remained high for a long period of time. Similar results for volume loss, seepage and temperature were found for the chopped sugar beets co-ensiled with chopped straw.

The high temperature measurements were a clear indication that the silos were not airtight, allowing oxygen into the silo to sustain the heat-forming processes. The average dry matter loss of nearly 40% was also a clear indication of aerobic decomposition during silage. Based on these results, the estimated biogas production cost of sugar beets was very high.

Further research is now underway to improve the silage of sugar beets to reduce dry matter loss and lower the estimated biogas production cost. Watch this space for updates!

For more information about storage of agricultural feedstocks, or if you have any questions regarding biomass renewable energy, please contact us.